The blood-brain barrier, which restricts the exchange of materials, is known to exist between the blood and the brain. This is presumably based on events in which: cerebrovascular endothelial cells form tight junctions with very narrow intercellular gaps; and the cells themselves perform the selective uptake and excretion of materials.
The blood-brain barrier has high penetration selectivity, which rarely permits materials, except for some materials (e.g., alcohols, caffeine, nicotine, and glucose), to cross the blood-brain barrier. This makes it difficult to treat brain diseases with brain therapeutic drugs, to diagnose brain diseases with brain diagnostic drugs, or to image the brain with contrast media.
A technique of delivering antibodies to the brain has been developed through the use of the property of glucose of crossing the blood-brain barrier (Patent Literature 1). This technique, however, merely glycosylates antibodies and exhibits only limited effects.